While flying today the heat shield on the bottom side of the top cowling on my sportcub detached from the adhesive and blocked off the airflow on the left side of the engine. I checked the area during preflight(for Bird's nest) and flew 12 minutes to get fuel. After topping off I always check fuel sumps for water. As I was walking around I saw the the heatsheild adhesive had come loose and the thin layer of shielding had folded down over the left side of the engine. I pushed it back up and it stayed for the return flight but it is something to be conscience of during preflight. Anybody got any ideas of the best adhesive to use to ensure good bonding with cowling???